Periodically dry-back Scotch boilers require replacement of the refractory material used as insulation in the hot gas reversing area located between the first pass furnace cylinder and the second pass tubes. In the past the refractory material has been formed of heavy brickwork or cast refractory cement which has been formed on, and secured to, the rear access door of the boiler.
Replacement has required the removal of the rear access door and removal and replacement of the refractory material by hand. Using a portable crane, a boiler repair service must remove the heavy rear door, lay it flat on the floor, break out the old refractory, form and cast the new, and allow at least two days for the cement to cure. Then the door must be reinstalled and the boiler fired gently until the refractory has fully cured. This whole process can take as much as three or four days, requires considerable down time, and can be a serious problem if it occurs during the heating season or if an industrial process must be interrupted.